Method of assembling observatory dome



June 11, 1968 w. "r. CLARK 3,387,356

METHOD OF ASSEMBLING OBSERVATORY DOME FiledMarch 22, 1966 2 Sheets-Sheet 1 Fig.1

William 7'. Clark INVENTOR.

June 11, 1968 w. T. CLARK METHOD OF ASSEMBLING OBSERVATORY DOME Filed March 22, 1966 2 Sheets-Sheet 2 William 7'. Clark INVENTOR.

United States Patent 3,387,356 METHOD OF ASSEMBLING OBSERVATORY DGME William T. Clark, PA). Box 885, Jackson, Miss. 39205 Continuation-impart of application Ser. No. 205,980,

June 28, 1962. This application Mar. 22, 1966, Ser. No. 5%,353

2 Claims. (Cl. 29-471.7)

This application is a continuation-in-part of US. Ser. No. 205,900, now Patent No. 3,245,178, granted Apr. 12, 1966. This invention involves a novel method of assembling a spherical sheet metal dome and more particularly pertains to a novel method of assembling an astronomical observatory of the rotatable dome type.

Observatory domes of the general nature described are frequently provided with interiorly disposed skeletal structures to which an outer skin of sheet metal is rigidly secured. While it is generally true that such a mode of construction results in a dome of high structural strength it will nevertheless be appreciated that such a mode of construction is time-consuming, relatively expensive and unduly heavy. With regard to the latter disadvantage, the relatively heavy weight of such a dome accentuates the problems attendant to the design and construction of a suitable supporting structure and rotating means.

It is therefore a primary object of this invention to provide an improved method of assembling a relatively lightweight observatory dome of sufficient structural strength so as to be ideally suited for housing astronomical telescopes without the necessity of utilizing massive supporting or rotating means.

Another object of the present invention is to provide a novel method of assembling a relatively rigid heet metal dome of hemispherical shape which method of assembly will result in the production of a lightweight, strong dome capable of readily compensating for stresses and strains caused by expansion and contraction of the dome brought about by temperature variations and the like.

A further object of the present invention is to provide a lightweight, compact observatory dome which is assembled in such a manner so as to provide a dome substantially devoid of interior reinforcing ribs wherein the necessary rigidity for a dome constructed in accordance with the present invention is provided by exteriorly disposed ribs which also cooperate to provide expansioncontraction joints between substantially all of the spherical sheet metal segments or gore comprising the hemispherical dome.

Still another object of the present invention is to provide a novel method for the assembly of a hemispherical dome or the like wherein the sheet metal segments com prising the dome are provided with upstanding outwardly disposed contiguous marginal flanges which flanges are united to form strengthening ribs by compressively clamping adjacent flanges so as to align the segments after which the adjacent clamped flanges are temporarily but releasably joined such as by spot-welds spaced along the arcuate length thereof. The compressive clamping means is then removed and the upstanding outwardly disposed contiguous edges of the adjacent flanges are autogenously united with a suitable arc-welding device provided with means for shielding the weld site with an inert gas. The heat attendant the autogenous welding of the flanges is suflicient to cause the previously applied spot-welds to fail thus producing an expansion-contraction joint between the adjacent sheet metal segments comprising the dome thus assuring that the dome will not be adversely affected by temperature changes and the like.

Still a further object of the present invention is to provide a novel method of assembling an observatory dome or the like by assembling a hemispherical dome in quadrispherical sections so as to facilitate shipment of the otherwise complete dome to the erection site where the quadrispherical sections are mated by utilizing a novel joint so as to form the complete hemispherical dome, which method of assembling the completed dome substantially obviates the presence of inwardly disposed strengthening ribs thus resulting in a substantially smooth inner surface for the dome.

Still a further object of the present invention is to provide a novel method of assembling an observatory dome devoid of any internally disposed reinforcing ribs wherein the sheet metal segments being joined are temporarily supported on a jig device characterized by a convex surface which surface represents a segmental portion of the desired arcuate configuration of the dome, thereby assuring that the sheet metal segments comprising the dome may be accurately aligned so as to facilitate construction of a pair of quadrisphercs to be used to form a hemispherical dome.

These together with other objects and advantages which will become subsequently apparent reside in the method of assembling a dome or sphere as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout and in which:

FIGURE 1 is a perspective view showing a typical observatory dome constructed in accordance with the principles of this invention wherein the shutter panels are shown in their open position;

FIGURE 2 is an enlarged perspective view of a convex jig utilized to align a plurality of the sheet metal segments so as to facilitate joining the segments by the method of the present invention to form the hemispherical dome shown in FIGURE 1;

FIGURE 3 is an enlarged fragmentary vertical crosssectional view showing a manner of compressively clamping the upstanding marginal flanges of adjacent segmental sections preparatory to temporarily joining the sections;

FIGURE 4 shows the upstanding flanges of FIGURE 3 being temporarily joined as by spot welding;

FIGURE 5 shows the spot-welded flanges of FIGURE 4 being autogenously joined at their outwardly disposed edges by utilizing an inert gas shield arc-welding device;

FIGURE 6 shows the completed joint between adjacent sheet metal segments after welding as in FIGURE 5, further showing that the spot-weld bond as shown in FIGURE 4 has been broken by the autogenous welding step thus producing an expansion-contraction joint between the adjacent segments; and

FIGURE 7 is a cross-sectional view of a joint utilized to join quadrispherical sections of a dome to form a hemispherical dome without necessitating the utilization of inert gas shielded welding equipment at the dome erection site. I

Referring now to the drawings in particular, FIGURE 1 shows a preferred embodiment of a rotatable observatory dome indicated generally at 10 constructed in accordance with the method of the present invention and shown mounted upon an upstanding annular foundation or wall 12 which is in turn carried by a suitable supporting structure 14 such as a building or the like. As shown in FIGURE 1, the observatory dome 10 includes a hemispherical dome 16 which is rotatably mounted upon the annular support 12 for rotation preferably throughout 360 about a generally vertical axis.

Inasmuch as the structure of the rotating means is shown in detail in the above-mentioned patent and inasmuch as such rotating means does not comprise a portion of this invention it has not been considered necessary to illustrate such means.

The substantially hemispherical dome 16 is assembled from a plurality of arcuate sheet metal segments 18 having exteriorly disposed upstanding marginal flanges 29 on opposed edges thereof. As will be discussed in detail hereinafter, the upstanding marginal flanges 20 are joined by a novel method to form the hemispherical portion 16 of the dome in a manner so as to provide an expansion-contraction joint between each of the segments 18. v

In the embodiment of the invention illustrated in FIG- URE 1 the observatory dome 10 is provided with a sight opening indicated generally at 22 which may be selectively closed by a pair of laterally movable shutters 24.

Briefly, the practice of the method of the present invention to assemble a sheet metal hemispherical dome involves placing a plurality of the arcuate sheet metal segments 18 in side-by-side position wherein the adjacent upstanding marginal flanges are in abutting relation. The marginal flanges 20 are then releasably fastened, in a manner to be described in detail hereinafter, after which the outer edges of the flanges 20 are joined, such as by autogenous welding for example, in a manner so as to permit the joints between adjacent arcuate segments 18 to function as expansion-contraction joints.

More specifically, referring now to [FIGURES 2-6, it will be seen that the arcuate segments 18 are preferably assembled in side-by-side relation on a convex form such as indicated generally at 24, the convex surface of which precisely corresponds to the arc of the dome 16 to be constructed. Although not shown or considered critical the segments 18 positioned upon the convex form 24 are preferably clamped to the form 24 so as to minimize distortion of the sheet metal segments 18 during the assembly thereof.

As seen best in FIGURES 2 and 3, the adjacent, but as yet unconnected, flanges 29 are compressively clamped such as by utilizing conventional vise-grip welders clamps 26 after which the abutting compressively clamped flanges 20 are releasably fastened adjacent the compressive clamp such as by spot welding with a suitable welding device indicated generally at 28. Although for purposes of illustration only two clamps 2-6 have been shown it will be understood that the upstanding marginal flanges 20 are clamped and then releasably joined such as by spot Welding at numerous spaced points such as indicated at along the length of the flanges 20, and generally the spot-welds are spaced approximately one inch apart along the arcuate length of the upstanding marginal flanges 20.

The nature of the bond between adjacent upstanding marginal flanges 20 at the spot-weld sites 30 is considered to be critical to the practice of the method of the present invention. Accordingly, when utilizing the conventional spot welding device 28, the current input to the spot-welder 28 must be carefully controlled so as to releasably bond the marginal upstanding flanges 20 on their contiguous surfaces adjacent the weld sites 30, i.e., that the initial bond must have sufltcient strength to permit removal of the compressive clamps such as 26 without permitting the bond to become disrupted, however, as will become clear hereinafter the strength of the bond at the weld site 30 must be of such low order that during the subsequent joining of the upstanding edges 32 of the marginal flanges 20 by autogenous welding the bonding of the flanges 20 adjacent the spot-weld sites 30' must be disrupted so as to no longer effectively join the flanges 20 at the spot-weld sites. Toward this end, it is normally preferable to remove surface accumulations from the adjacent faces of the abutting flanges 20 with a suitable agent such as denatured alcohol for example. It has been found that the use of alcohol facilitates spot welding of the flanges so as to releasably bond them, whereas utilization of a chemical agent to remove any interfering substance such as an oxide on the surface of the metal to be joined might result in a bond at the spot-weld site which did not tend to become disrupted during subsequent assembly steps. As will become more apparent it is imperative that the bonds at the spot-weld sites become disrupted during subsequent assembly steps.

In practice, all the segments 18 aligned on the form 24 are spot-welded in the manner set forth above after which the outer edges 32 of the upstanding marginal flanges 20' are permanently joined as shown in FIGURE 5 such as by utilizing an arc-welding head 40 having a non-consumable electrode 42, such as of tungsten, for example, wherein an arc is drawn between the outer edge 32 of the flanges 20 and the electrode while an inert gas, such as helium for example, is being supplied to the weld site about the electrode through the head 40, as is well-known in the art. In this manner, the upstanding flanges 20 are autogenou-sly bonded with a fusing weld extending along the entire upper edge 32 of the flanges 20.

The permanent bonding of the upstanding flanges 20 by autogenously welding the upper edges 32 such as at 44, as shown in FIGURE 5, must be done in such a manner so as to insure that the heat and stresses developed during the Heliarc-we-lding operation bring about the disruption of the bonds between the flanges 20 at the spot-weld sites 30 as may be seen in FIGURE 6 so as to insure that the-upstanding flanges 20 are secured only at their outer edges thus forming an expansion-contraction joint indicated generally at 50. As seen best in FIG- URE 6 the inwardly disposed adjacent faces of the upstanding flanges 20 are in slightly spaced apart relation thus permitting expansion and/or contraction of the arcuate sheet metal segments 18 comprising the dome 16 without adversely affecting the fusion welds 44.

Referring now to FIGURES 2 and 7 although not shown it will be understood that the generally hemispherical dome 16 is preferably fabricated from two quadrispherical portions wherein each of the quadrispheres is provided with a field joint such as illustrated in FIGURE 7 so as to facilitate shipment, handling and complete assembly of the dome at the erection site.

Toward this end, an arcuate metal plate 60 is rigidly secured, such as by continuously welding at 62, to the upstanding marginal flanges 20 of adjacent quadrispherical portions of the dome 16. As seen in FIGURE 7 the adjacent plates 60 comprising the field joint indicated generally at 59 are further provided with a plurality of apertures staggered along the length thereof, for the reception of suitable fasteners such as threadably secured bolts 64. In addition, a suitable resilient bead-type gasket 66 having an inwardly depending flange is preferably clamped between the upper ends of the plates 60 so as to provide a weather-tight seal for the field joint 59.

It will therefore be seen that the utilization of the field joint 59 permits assembly of the dome 16 from quadrispherical portions comprising one quarter of a sphere, for example, so as to facilitate shipment of the portions by rail or truck while permitting erection of a hemispherical dome at the erection site without necessitating the utilization of relatively complicated Heliarc equipment or disrupting the substantially smooth, unobstructed interior surface of the dome.

Accordingly, it may be seen that the method of the present invention facilitates the assembly of generally hemispherical sheet metal structures such as observatory domes and the like. Although not specifically discussed, it will be understood however that the method of the present invention could be extended to the assembly of generally spherical structures.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. A method of assembling an arcuate don-re comprising a plurality of arcuate sheet metal segments which comprises the steps of:

(a) providing a plurality of arcuate sheet metal segments of a sphere each having exteriorly disposed upstanding marginal flanges;

(0) placing the segments in side-by-side relation with adjacent flanges of adjacent segments being in faceto-face engagement while supporting the segments over a precision convex form the curvature of which corresponds to the desired curvature of the dome;

(c) applying compressive pressure to said adjacent flanges while releasably joining the flanges by spot Welding the flanges together at a plurality of points spaced along the length thereof; and

(d) autogenously fusing the outer edges of said adjacent reieasably joined flanges without fusing the spot welded areas whereby the heat required to fuse the flanges releases the spot-Welds thus providing expansion-contraction joints between adjacent segments.

2. A method of assembling a hemispherical dome c0mprising a plurality of dome portions each constructed of a plurality of arcuate sheet metal segments each segment having exteriorly disposed upstanding marginal flanges along a pair of opposite edges which method comprises the steps of:

(a) assembling each dome portion by placing a plurality of segments in side-by-side relation with adjacent flanges of adjacent segments bein in face-toface engagement while supporting the segments over a precision convex form the curvature of which corresponds to the desired curvature of the dome;

(b) applying compressive pressure to said adjacent flanges while releasably joining the flanges by spot welding the flanges together at a plurality of points spaced along the length thereof;

(0) autogenously fusing the outer edges of said adjacent releasably joined flanges Without fusing the spot welded areas whereby the heat required to fuse the flanges releases the spot-weld whereby the adjacent segments are joined along the outer edge of the flanges thus providing an expansion-contraction joint between adjacent segments; and

(d) securing an arcuate upstanding coextensive metal plate to the marginal flanges on opposite sides of each dome portion whereby two dome portions may be joined by securing adjacent plates with suitable mechanical fasteners so as to form a dome-shaped hemisphere.

References Cited UNITED STATES PATENTS 2,355,621 8/1944 Brown 29-4711 X 2,567,012 9/1951 Donelan 29-47l.7 X 3,044,152 7/1962 Stalker 29471.1 X 3,236,341 2/1966 Chopinet et a1 29-486 X 3,245,143 4/1966 Chopinet et al. 29-486 CHARLIE T. MOON, Examiner.

J. L. CLINE, Assistant Examiner, 

1. A METHOD OF ASSEMBLING AN ARCUATE DOME COMPRISING A PLURALITY OF ARCUATE SHEET METAL SEGMENTS WHICH COMPRISES THE STEPS OF: (A) PROVIDING A PLURALITY OF ARCUATE SHEET METAL SEGMENTS OF A SPHERE EACH HAVING EXTERIORLY DISPOSED UPSTANDING MARGINAL FLANGES; (B) PLACING THE SEGMENTS IN SIDE-BY-SIDE RELATION WITH ADJACENT FLANGES OF ADJACENT SEGMENTS BEING IN FACETO-FACE ENGAGEMENT WHILE SUPPORTING THE SEGMENTS OVER A PRECISION CONVEX FORM THE CURVATURE OF WHICH CORRESPONDS TO THE DESIRED CURVATURE OF THE DOME; (C) APPLYING COMPRESSIVE PRESSURE TO SAID ADJACENT FLANGES WHILE RELEASABLY JOINING THE FLANGES BY SPOT WELDING THE FLANGES TOGETHER AT A PLURALITY OF POINTS SPACED ALONG THE LENGTH THEREOF; AND (D) AUTOGENOUSLY FUSING THE OUTER EDGES OF SAID ADJACENT RELEASABLY JOINED FLANGES WITHOUT FUSING THE SPOT WELDED AREAS WHEREBY THE HEAT REQUIRED TO FUSE THE FLANGES RELEASES THE SPOT-WELDS THUS PROVIDING EXPANSION-CONTRACTION JOINTS BETWEEN ADJACENT SEGMENTS. 